Production of magnetic sound tape



July 31, 1956 w. 0. SPEED ET AL PRODUCTION OF MAGNETIC SOUND TAPE Filed Dec. 21, 1950 W ENTOR @42 5}? d u kifa ATTORNEYS United States. Patent PRODUCTION OF MAGNETIC SOUND TAPE William C. Speed, Riverside, and Harold J. Southcomb, Stamford, Conn., assignors to Audio Devices, Inc., New York, N. Y., a corporation of New York Application December 21, 1950, Serial No. 201,977

1 Claim. (Cl. 117-7) This invention relates to the production of magnetic recording tape and has for its object certain improvements in the method of and apparatus for precoating tape base with an adhesive material so that it will more readily receive and hold a coating of magnetic material.

This application is a division of copending applications, Serial Nos. 201,974 and 201,975 which is now Patent No. 2,700,367, issued January 25, 1955, both having been filed December 21, 1950, simultaneously herewith. In accordance with the disclosures therein contained, tape base is passed while under tension successively through a series of zones to obtain the magnetic recording tape. Thus, the tape base is moved from a charging zone to an adhesive precoating zone, through a precoat drying zone, a magnetic coating zone and one or more drying zones, etc. The subject matter of the present application is confined to the improvements relating to the adhesive precoating and precoat drying operations.

It has heretofore been difficult satisfactorily to apply conventional coatings of magnetic material, such as magnetic oxide of iron, on conventional tape base, such as paper, cellulose acetate. When, therefore, the magnetic coating material cannot be readily applied and does not properly adhere to the tape base it is advisable to apply a light coating or dressing of suitable adhesive material such as a copolymer of polybutadiene with acrylonitrile, the methyl esters of acrylic acid, etc., to the tape base in advance of the magnetic coating step. The adhesive coating, moreover, is partially dried advantageously to remove some of its solvent before the magnetic coating is applied.

These and other features of the invention will be better understood by referring to the accompanying drawing, taken in conjunction with the following description, in which:

Fig. 1 is a side elevation of a form of apparatus diagrammatically illustrating a practice of the invention; and

Figs. 2, 3 and 4 are enlarged views of the tape base precoating portion of the apparatus, Fig. 2 being a sectional view on the line 2-2 of Fig. 3, Fig. 3 a sectional plan of the line 3-3 and Fig. 2 and Fig. 4 a fragmentary sectional elevation showing the adhesive feed hopper, tape base and its guide supports.

A platform extends across and is secured to a frame 12. A laterally disposed guide rod 14 extends across the near end of the platform, being secured at its ends to vertical supports 16 and 18 in turn secured to the platform. As more clearly shown in Fig. 2, a pair of parallel supports 20 and 22 are secured to the platform. The supports are positioned respectively adjacent the opposite sides of the horizontally disposed discharge opening 24 of a feed hopper 26 secured at its rear upper portion to a vertically adjustable bracket 27. The ends of the bracket are provided with vertical passageways fitted with a pair of vertically disposed rods 28 and 30 integrally secured at their lower ends to the platform. The lower unthreaded ends of the rods are fitted with a coiled spring 32 and the upper threaded ends are fitted with nuts 34 and 36. This construction permits vertical adjustment of the feed hopper. The nuts may be suitably turned separately to elevate or lower each end of the hopper and hence to adjust its position with respect to the tops of parallel guide supports 20 and 22 and the top of the tape base.

The top of the hopper is provided with a removable cover 40, through which extends a conduit 42, with a regulating valve 44, depending from a container 46 of suitable free-flowing liquid adhesive material 48. The container rests on an annular cushion 50 carried by a support 52 attached to the frame.

As more clearly shown in Fig. 4, discharge opening 24 of the hopper is positioned slightly below the top level of parallel guide supports 20 and 22. This depresses moving tape base slightly into the space between the supports, thus causing it to wipe against the bottom of the hopper. Since only a very thin coat 62 of adhesive material is desired, this wiping action is sufiicient to provide it. As shown in Fig. 3 narrow side portions 64 and 66 of the tape base extend slightly beyond the ends of the discharge opening of feed hopper 26 and hence do not receive the adhesive material.

The precoat drying device is in the form of an elongated tunnel 70 enclosed by a bottom, side walls and a glass covered top 72; the ends of the tunnel being open so that the tape base may pass therethrough while suspended and out of contact with the walls. A plurality of heating devices 74, such as infrared lamps, are mounted directly above the glass covered top; the lamps being suspended from an electric conduit 76 in turn supported by vertical posts 78 attached to the frame.

Radiant heat is passed through the glass covered top onto the coated top of the tape base passing through the tunnel. As the adhesive precoat comes from the precoating machine, it is generally more liquid or less viscous than is desired for the subsequent coating operation with magnetic material. Some of the solvent, therefore, is advantageously volatilized from the adhesive precoat in the precoat drying zone while the tape base moves in its path of travel over guide support 80 to the magnetic coating zone.

It will be clear to those skilled in this art that the above is only by way of example, and that the practice of the invention readily lends itself to a number of useful modifications.

We claim:

In the method of producing magnetic sound-recording and sound-reproducing tape by passing a relatively long and narrow non-magnetic tape base while under tension to and through a magnetic coating zone to receive a liquid dispersion of free-flowing finely-divided magnetic material, which comprises moving the tape base while under tension in a predetermined path of travel to and through an adhesive precoating zone in advance of the magnetic coating zone, bringing the intermediate transverse portion only of one side of the tape base in wiping engagement with a transverse source of free-flowing adhesive liquid from the class consisting of a copolymer of polybutadiene with acrylonitrile and a methyl ester of acrylic acid to provide a very thin even layer thereof on the surface of the intermediate transverse portion, partially drying the resulting adhesive coating by volatilizing solvent therefrom while the tape base advances from the adhesive precoating zone to the magnetic coating zone, passing the partially dried tape base through the magnetic coating zone, and applying a layer of the liquid dispersion of finely-divided magnetic material on the partially dried adhesive coating to bind the magnetic coating more firmly thereon, the adhesive coating liquid being compatible with the non-magnetic tape base and the magnetic coating material so that the References Cited in the file of this patent UNITED STATES PATENTS Ostenberg May 13, 1924 Hansen Aug. 16, 1932 Van Voorhis Aug. 8, 1933 4 Perkins Nov. 14, 1933 Meyer Feb. 20, 1934 Hutchman Sept, 10, 1935 Nash Mar. 7, 1939 Quinn June 15, 1943 Bosomworth July 4, 1950 Schrnelzle Aug. 19, 1952 

